第一章 汽车总论
1) Today’s average car contains more than 15,000 separate, individual parts that must work
together. These parts can be grouped into four major categories: body, engine, chassis and electrical equipment 。 P1
现在的车辆一般都由15000多个分散、独立且相互配合的零部件组成。这些零部件主要分为四类：车身、发动机、底盘和电气设备。
2) The engine acts as the power unit. The internal combustion engine is most common: this
obtains its power by burning a liquid fuel inside the engine cylinder. There are two types of engine: gasoline (also called a spark-ignition engine) and diesel (also called a compression-ignition engine). Both engines are called heat engines; the burning fuel generates heat which causes the gas inside the cylinder to increase its pressure and supply power to rotate a shaft connected to the power train. P3
发动机作为动力设备，常见的类型是内燃机，其原理是通过发动机缸内的液体燃料燃烧而产生能量。发动机可分为两类：汽油机（点燃式）和柴油机（压燃式），都属于热力发动机。燃料燃烧产生热量使缸内气压上升，产生的能量驱动轴旋转，并传递给动力传动系。
第二章 内燃机
1) Power train system: conveys the drive to the wheels 2) Steering system: controls the direction of movement 3) Suspension system: absorbs the road shocks
4) Braking system: slows down the vehicle P4
传动系把发动机输出的扭矩传递给驱动轮。传动系包括离合器（对应机械变速器）或液力变矩器（对应液力自动变速器）、变速器、驱动轴、主减速器、差速器和驱动桥。
5) Drum brakes have a drum attached to the wheel hub, and braking occurs by means of brake
shoes expanding against the inside of the drum. With disc brakes, a disc attached to the wheel hub is clenched between two brake pads. P6
鼓式制动器的制动鼓和轮毂连接，制动蹄张开压紧制动鼓内侧从而产生制动。在盘式制动器上，连着轮毂的制动盘被紧紧夹在两个制动块之间。
1) Linking the piston by a connecting rod to a crankshaft causes the gas to rotate the shaft
through half a turn.The power stroke\the burnt gas and recharge the cylinder with a fresh petrol-air mixture:this control of gas movement is the duty of the valves;An inlet valve allows the mixture to enter at the right time and an exhaust valve lets out the burnt gas after the gas has done its job . P10 活塞通过连杆和曲轴连接，使得气体带动曲轴旋转半圈。作功冲程耗尽了所有的气体，这样就必须采取相应的措施排出废气并且向气缸内充入新的可燃混合气：气体的运动由气门来控制。进气门使可燃混合气在恰当的时刻进入气缸，排气门使燃烧后的废气排出气缸。 2) The spark-ignition engine is an internal-combustion engine with externally supplied in
ignition,which converts the energy cntained in the fuel to kinetic energy.The cycle of operations is spread over four piston strokes. To complete the full cycle it takes two revolutions of the crankshaft. P11
火花点火式发动机是由外部提供点火的内燃机，从而将含在燃料内的能量转化成动能。发动机的一个工作循环分布在活塞的四个行程中，一个完整的工作循环曲轴需要转动两圈。 3) The oil pump in the lubricating system draws oil from the oil pan and sends it to all working
parts in the engine. The oil drains off and runs down into the pan. Thus,there is constant circulation of oil between the pan and the working parts of the engine. P15
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润滑系的机油泵从油底壳抽出机油，并把机油输送给发动机的所有工作部件。机油从油底壳流进流出。因而在油底壳和发动机的工作部件之间有机油定向循环流动。
4) Most pistons are made from cast aluminum. The piston, through the connecting rod,
transfers to the crankshaft the force created by the burning fuel mixture. This force turns the crankshaft. P17
大多数活塞由铝铸造而成。通过连杆，活塞把可燃混合气燃烧所产生的力传递给曲轴，并带动曲轴旋转。
5) When the engine runs in compression stroke and power stroke, the valves must close tightly
on their seats to produce a gas-tight seal and thus prevent the gases escaping from the combustion chamber. If the valves do not close fully the engine will not develop full power. Also the valve heads will be liable to be burnt by the passing hot gases, and there is the likelihood of the piston crown touching an open valve, which can seriously damage the engine. P28
当发动机在压缩冲程和作功冲程工作时，气门必须紧贴在气门座上，形成良好的气密性以防止燃烧室漏气。如果气门关闭不严，发动机就不能发挥出全部的功率。而且气门头部容易被经过的高温气体烧蚀，活塞顶部也可能会碰到气门使发动机严重损坏。
6) So that the valves can close fully some clearance is needed in the operating mechanism.
This means that the operating mechanism must be able to move sufficiently far enough away from the valve to allow the valves to be fully closed against its seat by the valve spring. However, if the clearance is set too great this will cause a light metallic tapping noise.
所以在气门传动机构中要预留一些间隙使气门得以完全关闭。这就是说，气门传动机构 运动要与气门有一个充分远的距离，使得气门在气门弹簧作用下紧闭气门座。可是如果 间隙过大，会引起轻微的金属敲打声。
7) Definition: The time at which valves open and close and the duration of valves opening is
states in degrees of camshaft rotation.
气门从开启到关闭所经历的曲轴转角，称为配气相位。
8) It is apparent from this description that the exhaust valve stays open for a short period of
time during which the intake valve is also open. In other words, the end of the exhaust stroke and the beginning of the intake stoke overlap for a short period of time. This is called valve overlap. Valve timing and valve overlap vary on different engines.
由上显而易见，排气门在进气门打开的一小段时间内也打开着。换句话说，排气冲程终了和进气冲程初期有一小段时间的重叠，这称为气门重叠。不同的发动机，其配气相位和气门重叠是不一样的。
9) Opening the intake valve before TDC and closing it after BDC increases the fill of air-fuel
mixture in the cylinder. Opening the intake valve early helps overcome the static inertia of the air-fuel mixture at the beginning of the intake stroke, while leaving the intake valve open after BDC takes advantage of the kinetic inertia of the moving air-fuel mixture. This increases volumetric efficiency.
在上止点前打开进气门和在下止点后关闭进气门可增加气缸内可燃混合气的进气量。提前打开进气门有助于克服进气冲程初期的惯性，同时在下止点后打开进气门可充分利用可燃混合气运动时的惯性，这可增加容积效率。
10) Each cam must revolve once during the four-stroke cycle to open a valve. A cycle,
remember, corresponds with two revolutions of the crankshaft. Therefore, the camshaft must revolve at exactly half the speed of the crankshaft. This is accomplished with a 2:1 gear ratio. A gear connected to the camshaft has twice the number of teeth as a gear
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connected to the crankshaft. P29
在一个四冲程的循环里，每个凸轮转动一次来打开一个气门。在一个循环里曲轴是转动两圈的。因此，凸轮轴正好以曲轴转速的一半旋转，这是由2:1的传动比来实现的。连接凸轮轴的齿轮齿数是连接曲轴的齿轮齿数的两倍。
11) Gasoline must vaporize easily. This characteristic, called volatility, is important. However, it
must not vaporize too easily, or it will turn to vapor inside the fuel tank or fuel lines. Inside the fuel line, fuel vapor may block the flow of liquid gasoline. This is called vapor lock. Vapor lock is common in fuel lines where the inlet side of the pump is exposed to high temperatures. P33
汽油应易于蒸发，这个重要的特性称为挥发性。但是汽油也不能挥发得过快，不然它会在油箱或油管里转变为蒸气。在油管中汽油蒸气会阻碍液态汽油的流动，这称为气阻。汽油泵的入口处承受着高温，就经常出现气阻。
12) Increasing the pressure of the fuel mixture in the combustion chamber before ignition helps
to increase the power of an engine. This is done by compressing the fuel mixture to a smaller volume. Higher compression ratios not only boost power but also give more efficient power. But as the compression ratio goes up, knocking tendency increases. P33 在点火前增加燃烧室内可燃混合气的压力有助于提高发动机的功率，这是通过把可燃混合气压缩到一个极小的体积来实现的。高的压缩比不仅增加发动机的功率，而且会带来更多的有效功率。但随着压缩比的增加，爆震的可能性也会增加。
第三章 传动系统
1) When a vehicle is to be moved from rest the clutch must engage a stationary gearbox shaft
withthe engine; this must be rotating at a high speed to provide sufficient power or else the load will be too great and the engine will stall (come to rest). P72
当汽车原地起步时，离合器要将静止的变速器轴同发动机接合起来，此时发动机必须高速旋转以提供足够大的功率，否则载荷过大将引起发动机熄火。
2) The driving member consists of two parts: the flywheel and the pressure plate. The flywheel
is bolted directly to the engine crankshaft and rotates when the crankshaft turns. The pressure plate is bolted to the flywheel. The result is that both flywheel and pressure plate rotate together. P74
主动部分由飞轮和压盘两部件组成。飞轮用螺栓直接连接到发动机曲轴上，随曲轴旋转而旋转。压盘与飞轮连接，这样飞轮和压盘一起旋转。
3) The driven member, or clutch disc, is located between the flywheel and pressure plate. The
disc has a splined hub that locks to the splined input shaft on the gearbox. Any rotation of the clutch disc turns the input shaft.
从动部分（或从动盘）位于飞轮和压盘之间。从动盘上有花键毂，连接着变速器上带花键 的输入轴。从动盘的旋转带动变速器输入轴随之转动。
4) The inner part of the clutch disc, called the hub flange, has a number of small coil springs.
These springs are called torsional springs. They let the middle part of the clutch disc turn slightly on the hub. Thus, the springs absorb the torsional vibrations of the crankshaft. When the springs have compressed completely, the clutch moves back until the springs relax. In other words, the clutch absorbs these engine vibrations, preventing the vibrations from going through the drive train.
当从动盘的内侧有一些叫作扭转弹簧的小螺旋弹簧，这些弹簧使得从动盘中部相对从动盘毂能有轻微转动，从而吸收曲轴的扭转振动。压紧弹簧完全压缩时，离合器向后移动直到弹簧开始伸张为止。也就是说，离合器吸收发动机的振动，防止振动传递给传动系。
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5) These are the parts that release pressure from the clutch disc. The operating members
consist of the clutch pedal, clutch return spring, clutch linkage, clutch fork, and throwout bearing. The clutch linkage includes the clutch pedal and a mechanical or hydraulic system to move the other operating members.
操纵机构释放离合器盘的压力。操纵机构由离合器踏板、回位弹簧、离合器杆系、分离叉和分离轴承等组成。离合器杆系包括离合器踏板以及用来操纵其它部件的机械式或液压式操纵系统。
6) When the clutch pedal is depressed, the clutch linkage operates the clutch fork. The clutch
fork, or release fork, moves the throwout bearing against the pressure plate release levers. These levers then compress springs that normally hold the clutch disc tightly against the flywheel.
踩下离合器踏板，离合器杆系操纵分离叉。分离叉带动分离轴承压向压盘上的分离 杠杆，分离杠杆压缩压紧弹簧。通常情况下，压紧弹簧使从动盘和飞轮紧密接合。 7) When the clutch pedal is released, the pressure plate forces the clutch disc against the flywheel. The clutch return spring helps raise the pedal.
释放离合器踏板，压盘使从动盘同飞轮接合，回位弹簧使离合器踏板抬起。 8) The modern automobile engine is a powerful, lightweight, and dependable powerplant. However, it is not perfect for three reasons. P77
新型的汽车发动机动力强劲、质量轻便而且性能可靠。然而它有三个美中不足的原因。 9) In simple terms, a gearbox multiplies engine torque and --- through gears--- sends that
power to the drive axle. A driver shifts or changes the gears to increase or decrease the torque produced by the engine.
简而言之，变速器利用齿轮扩大发动机的扭矩，向驱动桥传递动力。驾驶员通过换挡来升高或降低发动机的输出扭矩。
10) The suspension connects the final drive assembly to the car body. The final drive moves up
and down in relation to the engine and transmission. A coupling is needed that permits movement between the final drive and transmission. The universal joints (U-joints) and sliding joints provide this coupling. P94
悬架连接着主减速器总成和车身。主减速器相对于发动机和变速器上下运动，这样在主减速器和变速器之间就需要万向节和滑动联轴节等连接装置来允许其相对运动。
11) A shaft which receives the drive from a cross type joint varies its speed during rotation; the
greater the drive angle the greater the speed variation. A constant rotational speed can be restored by fitting a second joint in a way such that when the first joint increases its speed the second joint decreases its speed. P95
传动轴接收十字轴式万向节传来的动力，转动时其速度发生变化。传动角越大，速度变化越大。要实现等速，必须以某种方式安装第二个万向节，这样第一个万向节使转速增大，第二个万向节就使转速减少。
12) The hypoid gear is in common use today due mainly to the fact that the offset pinion allows
the propeller shaft to be set below, (for cars) or above, (for commercial vehicles) the crown wheel center. This gives either a reduction in the propeller shaft tunnel, which causes a bump in the vehicle floor, or in the case of a commercial vehicle a reduction in the angle through which the universal joint has to operate. P96 现在的主减速器普遍使用准双曲面齿轮，这主要是因为主动锥齿轮的偏移允许轿车上传动轴布置得比从动锥齿轮低一些，而商用车上又允许布置得比从动锥齿轮高一些。这就使得传动轴管状盖板(它会导致汽车车身地板形成凸起)位置降低，或者使得商用车上万向节工作角度减小。
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13) Large crown wheels reduce the ground clearance under the differential. In the case of pinion
axles and planetary- hub reduction axles, the differential and the half-shafts can be made smaller by splitting the reduction. This makes it possible, even in the case of high power outputs, to achieve sufficient ground clearance of the vehicle.
从动锥齿轮尺寸大，就降低了汽车的离地间隙。如果采用圆柱齿轮式和行星齿轮式轮边减速器，通过两级减速的形式可极大减小差速器和半轴的尺寸。这样，汽车就可以获得足够大的离地间隙， 即使输出功率要求较大也可以。
14) When a vehicle is cornered the inner wheel moves through a shorter distance than the outer
wheel. This means that the inner wheel must slow down and the outer wheel must speed up. During this period it is desirable that each driving wheel maintains its driving action. The differential performs these two tasks. P98
当汽车转弯时，内侧车轮比外侧车轮行驶的距离要短，这说明内侧车轮比外侧车轮转得要慢。在此期间，维持每个驱动车轮的行驶状态是很重要的。这两个任务由差速器来完成。 15) When the vehicle is travelling straight, the lever will divide the driving force equally and
both discs will move the same amount. When the vehicle corners, the driving force will still be divided equally but the inner disc will now move through a smaller distance; this will cause the lever to pivot about its center which will prize forward the outer disc to give it a greater movement. This action shows that the torque applied to each driving wheel is always equal --- hence the differential is sometimes called a torque equalizer.
汽车直行时，杠杆平均分配驱动力，两个圆盘移动相同的距离。汽车转弯时驱动力仍然会平均分配，但是内侧圆盘移动的距离要小一些，这使得杠杆绕中心转动，推动外侧圆盘使之移动更大的距离。这个过程表明扭矩总是平均分配给每个驱动轮，因此差速器有时也叫做扭矩平衡装置。
第四章 制动系统
1) Energy is required when a vehicle is accelerated from rest to a certain speed. A proportion
of that energy is now stored in the vehicle and is called kinetic energy. In order to reduce the speed of the vehicle, the brakes have to convert the kinetic energy to heat energy; the speed of conversion governs the rate at which the vehicle slows down. P102
汽车从原地起步加速到某一速度需要能量。储存在汽车中的那部分能量称为动能。要降低车速,制动器必须把汽车的动能转换为热能；转换的速度决定了汽车减速的快慢。
2) The three types of braking systems are in use today: service braking system, parking
braking system and additional retarding-braking system. The service braking system and the parking braking system have separate control and transmission devices. The service braking system is normally foot-operated, while the parking braking system is hand-operated.
目前使用的制动系统有三种类型：行车制动系，住车制动系和辅助制动系．行车制动系和住车制动系有独立的控制和传动装置．行车制动系通常使用脚刹，而驻车制动系通常使用手刹．
3) Two types of brakes are used in modern cars: drum brakes and disc brakes. Since 1976, all
cars have used disc brakes on the front wheels. Most cars use drum brakes on the rear wheels . In both drum and disc brakes, a hydraulic system applies the brakes. The hydraulic system connects the brake pedal to the brake parts at each wheel.
目前使用的制动器有两种类型：鼓式制动器和盘式制动器．从1976年开始，所有的汽车前轮都使用盘式制动器,大部分汽车后轮使用的是鼓式制动器. 在盘式制动器和鼓式制动器中都使用液压系统. 液压系统把制动踏板与每个车轮的制动部件相连接.
4) These have two shoes, anchored to a stationary back-plate, which are internally expanded to
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